Adiabatic shear band induced chip serration in high speed machining
Résumé
A number of studies have been carried out on the optimization of the cutting process notably on the titanium alloy Ti-6Al-4V. Molinari et al. [JMPS, 2013] carried out numerical and analytical investigations about the role of cutting conditions on adiabatic shear banding and chip serration during the high speed orthogonal cutting of Ti-6Al-4V. Here we extend their parametric study by performing numerical analyses of the effect of (i) plastic dissipation induced self-heating and (ii) the material failure triggered by a critical strain value. It is shown that the chip morphology is strongly dependent on the arbitrary values given to the inelastic heat fraction β (Fig.1) and the critical strain to failure. In order to render the model independent of such arbitrary criteria, a physics- motivated 3D large deformation model based on irreversible thermodynamics [Longère et al., JEMT, 2009] is proposed to reproduce the shear band consequences in the context of high speed metal cutting. This model accounts for the coupled effects of dynamic plasticity, strain localization and micro-voiding.